US2501032A - Permanent magnet assembly for electrodynamic loud-speakers - Google Patents

Permanent magnet assembly for electrodynamic loud-speakers Download PDF

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Publication number
US2501032A
US2501032A US632065A US63206545A US2501032A US 2501032 A US2501032 A US 2501032A US 632065 A US632065 A US 632065A US 63206545 A US63206545 A US 63206545A US 2501032 A US2501032 A US 2501032A
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United States
Prior art keywords
magnet
yoke
pole piece
disc
spring
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Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US632065A
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English (en)
Inventor
Fred J Harbaugh
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RCA Corp
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RCA Corp
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Filing date
Publication date
Priority to BE469578D priority Critical patent/BE469578A/xx
Application filed by RCA Corp filed Critical RCA Corp
Priority to US632065A priority patent/US2501032A/en
Priority to ES0175452A priority patent/ES175452A1/es
Application granted granted Critical
Publication of US2501032A publication Critical patent/US2501032A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R9/00—Transducers of moving-coil, moving-strip, or moving-wire type
    • H04R9/06—Loudspeakers
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R9/00—Transducers of moving-coil, moving-strip, or moving-wire type
    • H04R9/02—Details

Definitions

  • This invention relates to sound transducers and more particularly to a permanent magnet dynamic loudspeaker.
  • Anobject of the invention is to provide a new opening t* in the bottom of the cup.
  • a soft iron or mild steel inner pole piece Il is located upon the pole face or top surface of magnet l and the upper end of this pole piece cooperates with a and improved method and .means of assembly of 5 circular opening in yoke plate 3 in forming an magnetic elements of a loudspeaker. annular air gap.
  • This centering disc is formed with a to be characteristic of the invention are set iorth downward bias tendency as indicated by the dotwith particularity in the appended claims.
  • the ted line lil To improve the spring action the invention itself, however, both as to its fundacentral portion of the disc is preferably divided mental principles and as to its particular embodiinto independently acting segments, in the man ments will best be understood by reference to the ner disclosed in connection with Figure au.
  • the spring tension exerted which: downwardly by the disc l5 forces the pole piece Figure l is a cross sectional View in side eleil downwardly against the magnet l and mainvatios of a loudspeaker magnet structure, etc.
  • Figures 2 and 3 are side elevation fragmentary g5 relation.
  • friction. resulting from the views, partly in section, of a loudspeaker magpressure exerted by disc l5 is suicient to prevent net system embodying modied forms of 'the displacement of magnet l laterally relative to invention, elements l and Il, but to insure against undue
  • Figure l is a side elevation View in section of CSlDlaCSlll-ent Caused by dropping the lllt, limta loudspeaker magnet system embodying a modiing means ShOWn in Figures 4, 5 and 6 may be lied form of the invention, used.
  • the periphery of the base of the magnet Figure 4a is a plan view, reduced in size, of an l may be welded to the yoke l if desired.
  • element shown in Figure 4 and The unit may be assembled as follows:
  • the Figures 5 and Gare fragmentary views partly magnet l can be located in the position shown in section, reduced in size, of modifications emand the pole piece Il placed on top thereof as bodying the invention. indicated.
  • the yoke plate s can be dropped In the various figures like reference numerals into approximately the position shown and represent like parts.
  • apermanent magnet 'I of highretentivity 50 both as a centering disc and resilient clamping preferably Alnicoj composed of the following plate for holding the magnet elements in aselements, aluminum, nickel, cobalt, and iron.
  • This magnetic material is extremely hard, can-
  • a voice coil il is wound upon a cylindrical form not be drilled or tapped, at least 'by ordinary it the top end of which is closed by a diaphragm means, and is moldedn'short lengths.
  • the voice coil structure is flexibly supported per and lower pole faces of the magnet l are for ibratory movement by means oi a concenground flat and klie in parallel planes. ln this trically corrugated centering disc of librous modiiication, the magnet Vl -is provided with a material supported at its periphery by a ring 25,
  • the magnet 'l is centrally located upon the base of o Lhshape yoke as in Figures 4 and 5, and is preferably held in position as shown in these figures, described below.
  • the top of magnet l and is provided with a laterally extending iiange 29.
  • the yoke plate 3 is located upon the open end of yoke l in the same manner as shown in Figure 1.
  • the pole piece 21 is centered within the opening I3 of plate 3 by means of a relatively stiff centering disc I6, preierably of brass or phosphor-bronze, fastened permanently to plate 3.
  • a plurality of brass screws 3l are threaded in the disc l5 and extend up wardly 'through holes in plate 3 for turning to force the flange 29 downwardly against magnet 1, the clamping exerted axially by these screws 'and resiliency of the disc retaining the magneti-c elements in assembled relation.
  • the assembly of parts easy in this case and requires no special tools. The parts may be taken apart readily.
  • the centering disc and screws in other words, are retaining means for both centering and clampingr the magnetic members.
  • a cupshape element 38 as of brass, is inverted over the flange 31, under the screw ends, the lip extending downward around the top of the magnet to limit lateral shifting of the latter.
  • the magnet 3l and pole piece are of the usual solid type, used with a conventional irusto-conical type diaphragm 3S.
  • the nagnet 53 is a small cylindrical bloclr of Alnico V an alloy of much higher magnetic energy than the older forms of Alnico, an alloy composed of aluminum 8%, nickel 14%, cobalt 241%, copper 3% and the rest iron. Because of tb characteristics of the material, and high magnetic energy storage in. a small lightweight piece, the present clamping system is ideally suitable. It been found undesirable to provide a bore hole in the magnet for bolting purposes. It had been the custom in making the heavier and larger magnets of ordinary Alnico alloy to provide a The pole piece 2'! is located on central bore hole at the time of molding, for bolting parts together, as shown in Cunningham Patent 2,312,238 of February 23, 1943, but such an arrangement had been found undesirable with the new alloy magnets.
  • a yoke ⁇ plate 4l Figure 4 preferably rectangular, is welded to the ends of a U-shaped yoke 43.
  • the bottom face oi plate 4l is provided with a milled groove concentric with opening I3, into which ts the upper edge of a dished circular centering element preferably of phosphor-bronze, the groove securing the centering element against lateral movement.
  • This element is provided with a central. opening 41 accurately concentric with respect to opening i3 in the pole plate 4
  • Element 45 is preferably slit radially as shown at 46 in Figure 4a, to provide a plurality of independently biased spring segments to provide greater spring action and more circumferentially uniform pressure around Eil.
  • a pole piece 49, provided with a lower annular' flange l is assembled into approximately tl position shown by laterally inserting same relative to the yoke and upwardly into the po sition concentric with respect to and spaced from the opening i3 to form an air gap. Clamping too-,s are used during assembly to force the pole piece and spring element 45 upwardly slightly beyond the position shown and holding them in such position while the magnet 53 is inserted laterally into the position shown.
  • the base of magnet preferably ts into a slight depression 54 formed by milling or pressing, to insure against lateral displacement in the case of severe shocks, as from dropping the unit. It will be apparent, therefore, that this modiiication results in a substantial simplification and improvement.
  • a disc 55 is used for centering the pole pieces and a separate spring clamp 5l' is used ior pressing the magnetic elements together, as shown and claimed broadly in combination in Cunningham application Serial No. 532,654, filed concurrently herewith.
  • each end of the spring clamp 5i' is biased upwardly and outwardly, as shown in dotted lines, and when assembled, engages an abutment or offset shoulder 59 with a high degree oi compression, holding the elements firmly together as shown.
  • the assembly is accomplished simply by inserting the elements 49, 5l' and subsequently 53, with the spring tension relieved as the position shown in dotted lines.
  • FIG. 5 Another' feature of the Figure 5 modification is that several portions of the spring 51 are bent downwardly below flange 5l and annularly spaced closely around the top of the magnet 53 below the upper polar face for the purpose of limiting any lateral displacement of the magnet 53, as in Figure 3.
  • This avoids the use of a depression (Fig. 4) or other means on the yoke around the base of the magnet, or the use of a separate element as in Figure 3.
  • Ordinarily bolts, lugs, cement are used to anchor the magnet to prevent shifting, and in some cases the space between the magnet and yoke has been filled in with plastic molding material to hold all members together in a mass.
  • the portion of the eld yoke in contact with the magnet base may be ground to provide a smooth nat surface without any obstructions for ease of lateral assembly and providing an elcient contact area with the lower polar face of the magnet.
  • the centering disc 60 is made of relatively stiif nonmagnetic material, is fastened permanently to plate M, as by welding, and the inner opening counterbored concentrically relative to yoke plate opening I3, nts snugly around inner pole piece 129.
  • the resilient pressure effect is obtained in part or in entirety by separate means such as a soft rubber ring 58 heldin compression between the inner portion or the disc and the shoulder 5l on the base of the inner pole piece 49.
  • Limitation of lateral movement of the magnet 53 is effected by lancing out several tongues 56, say four spaced ninety degrees apart, radially from the disc and bending them partway downward, as shown in dotted lines, in radially spaced relation.
  • the disc serves for accurately centering the pole piece 49 concentrically with respect to the opening I3 in the plate 4I, for approximately centering the magnet, and cooperates with resilient means 58 for resiliently clamping the members 49 and 53 together and in place on the yoke, not shown, but similar in general to that of Figure 5.
  • Similar lateral limiting structure may be formed in disc l5 oi Figures l, 2 or 4.
  • rubber ring 58 may be discarded, and the centering disc engage the shoulder 5l, relying on the resiliency of the disc 60 to Clamp the magnetic members axially, as in Figure 1.
  • the disc with or without the rubber ring, may be termed resilient centering means having structure for limiting lateral displacement of said magnet.
  • a dynamic loudspeaker comprising in combination (1) a field structure including a field yoke and a yoke plate connected to said eld yoke, said yoke plate having a centrally disposed circular opening, (2) a magnet having upper and lower pole faces With said lower pole face disposed on said field yoke, (3) a pole piece having one end thereof disposed upon said upper pole face, said pole piece having its opposite end extending into said opening in spaced relation to said yoke plate thereby to provide an air gap therebetween, and (4) an annular, disc-like spring secured to said yoke plate, said spring embracing and engaging said pole piece to center it in said yoke plate opening, said spring being biased by engagement thereof with said pole piece in a direction such as to cause it to exert a force against said pole piece in an axial direction toward said magnet whereby said spring is effective to maintain said pole piece,
  • pole piece has an annular shoulder against which said spring exerts its force for securely holding said pole piece, said magnet and said field structure in assembled relation.
  • a lJ-shaped eld yoke of magnetic material having a base portion including a pole face intermediate the ends of said yoke, a yoke plate attached to said ends and provided with a circular opening, a permanent magnet having one end disposed upon said field yoke pole face, a pole piece having a lower pole face disposed upon the opposite end of said magnet and provided with an annular shoulder, spring means attached to said yoke plate and provided with an opening concentrically located with respect to said yoke plate opening, said spring means being of non-magnetic material and surrounding and engaging said pole piece for centering said pole piece within said yoke plate opening, said spring means being in contact with said annular shoulder and being biased by engagement thereof with said shoulder in a direction such as to Cause it to exert a force against said shoulder in an axial direction toward said magnet whereby said spring means is effective to securely hold said pole piece, said magnet and said yoke in assembled relation.
  • a dynamic loudspeaker comprising, in combination, (l) a field structure including a iield yoke and a yoke plate connected to said field yoke, said yoke plate having a centrally disposed circular opening, (2) a magnet having upper and lower pole faces with said lower pole face disposed on said field yoke, (3) a pole piece having one end thereof disposed upon said upper pole face, said pole piece having its opposite end extending into said opening in spaced relation to said yoke plate thereby to provide an air gap therebetween, and (-4) a sheet metal centering spring secured to said yoke plate, said spring embracing and engaging said pole piece to center it in said yoke plate opening, said spring being biased by engagement thereof with said pole piece in a direction such as to cause it to exert a force against said pole piece in an axial direction toward said magnet whereby said spring is eifective to maintain said pole piece, said magnet and said iield structure in assembled relation.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
  • Signal Processing (AREA)
  • Audible-Bandwidth Dynamoelectric Transducers Other Than Pickups (AREA)
US632065A 1945-11-30 1945-11-30 Permanent magnet assembly for electrodynamic loud-speakers Expired - Lifetime US2501032A (en)

Priority Applications (3)

Application Number Priority Date Filing Date Title
BE469578D BE469578A (es) 1945-11-30
US632065A US2501032A (en) 1945-11-30 1945-11-30 Permanent magnet assembly for electrodynamic loud-speakers
ES0175452A ES175452A1 (es) 1945-11-30 1946-10-25 UN ALTAVOZ DINáMICO DE IMáN PERMANENTE

Applications Claiming Priority (1)

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US632065A US2501032A (en) 1945-11-30 1945-11-30 Permanent magnet assembly for electrodynamic loud-speakers

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US2501032A true US2501032A (en) 1950-03-21

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Cited By (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2581223A (en) * 1947-03-04 1952-01-01 Voigt Paul Gustavus Ad Helmuth Permanent magnet system for loudspeakers
US2604551A (en) * 1947-10-02 1952-07-22 Magnavox Australia Pty Ltd Magnetic unit with magnetically positioned pole piece for loudspeakers
US2761913A (en) * 1953-02-18 1956-09-04 Gen Dynamics Corp Loudspeaker
US2772381A (en) * 1951-06-25 1956-11-27 Swing A Way Mfg Company Magnetic lid lifter for can openers
US2964597A (en) * 1954-12-10 1960-12-13 Rca Corp Loudspeaker magnetic field structure
US3092694A (en) * 1959-02-16 1963-06-04 Rca Corp Loudspeaker
US3106670A (en) * 1960-04-21 1963-10-08 Rca Corp Magnetic field structure for loudspeakers
US3801943A (en) * 1971-06-16 1974-04-02 J Bertagni Electoacoustic transducers and electromagnetic assembly therefor
US3874665A (en) * 1971-10-05 1975-04-01 Mcculloch Corp Ball putting cup and method of ejecting ball from same
US4635287A (en) * 1983-10-19 1987-01-06 Mutsuo Hirano Audio-frequency electromechanical vibrator
USRE32785E (en) * 1983-10-19 1988-11-15 Sanden Corporation Audio-frequency electromechanical vibrator
US4799266A (en) * 1986-11-25 1989-01-17 Kabushiki Kaisha Kenwood Electroacoustic converter
US20030219142A1 (en) * 2002-03-26 2003-11-27 Stompler Thilo Christian Speaker driver with detachable motor and basket

Citations (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1811367A (en) * 1929-03-27 1931-06-23 Magnavox Co Loud speaker
US1847702A (en) * 1931-05-02 1932-03-01 Bell Telephone Labor Inc Sound translating device
GB372809A (en) * 1931-02-04 1932-05-04 Edgar Allen & Company Ltd Improvements in or relating to permanent magnets
US1864809A (en) * 1930-01-08 1932-06-28 Magnavox Co Loud speaker
GB389898A (en) * 1931-11-03 1933-03-30 Darwins Ltd Improvements in or relating to permanent magnets
GB397617A (en) * 1932-05-13 1933-08-31 Everett Ross Dempster Loud speakers
GB412552A (en) * 1932-12-21 1934-06-21 Everett Ross Dempster Improvements in or relating to loud speakers
US1991738A (en) * 1931-01-05 1935-02-19 Rca Corp Acoustic device
US2029282A (en) * 1935-04-13 1936-01-28 Igor B Serge Magnetic circuit and construction thereof
FR827276A (fr) * 1937-01-07 1938-04-22 Perfectionnements aux haut-parleurs électrodynamiques
US2312238A (en) * 1938-01-27 1943-02-23 Rca Corp Dynamic loud-speaker
GB552328A (en) * 1941-12-04 1943-04-01 Reslo Sound Equipment Ltd Improvements in or relating to loud speakers and the like
US2395166A (en) * 1942-12-24 1946-02-19 Astatic Corp Transducer

Patent Citations (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1811367A (en) * 1929-03-27 1931-06-23 Magnavox Co Loud speaker
US1864809A (en) * 1930-01-08 1932-06-28 Magnavox Co Loud speaker
US1991738A (en) * 1931-01-05 1935-02-19 Rca Corp Acoustic device
GB372809A (en) * 1931-02-04 1932-05-04 Edgar Allen & Company Ltd Improvements in or relating to permanent magnets
US1847702A (en) * 1931-05-02 1932-03-01 Bell Telephone Labor Inc Sound translating device
GB389898A (en) * 1931-11-03 1933-03-30 Darwins Ltd Improvements in or relating to permanent magnets
GB397617A (en) * 1932-05-13 1933-08-31 Everett Ross Dempster Loud speakers
GB412552A (en) * 1932-12-21 1934-06-21 Everett Ross Dempster Improvements in or relating to loud speakers
US2029282A (en) * 1935-04-13 1936-01-28 Igor B Serge Magnetic circuit and construction thereof
FR827276A (fr) * 1937-01-07 1938-04-22 Perfectionnements aux haut-parleurs électrodynamiques
US2312238A (en) * 1938-01-27 1943-02-23 Rca Corp Dynamic loud-speaker
GB552328A (en) * 1941-12-04 1943-04-01 Reslo Sound Equipment Ltd Improvements in or relating to loud speakers and the like
US2395166A (en) * 1942-12-24 1946-02-19 Astatic Corp Transducer

Cited By (15)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2581223A (en) * 1947-03-04 1952-01-01 Voigt Paul Gustavus Ad Helmuth Permanent magnet system for loudspeakers
US2604551A (en) * 1947-10-02 1952-07-22 Magnavox Australia Pty Ltd Magnetic unit with magnetically positioned pole piece for loudspeakers
US2772381A (en) * 1951-06-25 1956-11-27 Swing A Way Mfg Company Magnetic lid lifter for can openers
US2761913A (en) * 1953-02-18 1956-09-04 Gen Dynamics Corp Loudspeaker
US2964597A (en) * 1954-12-10 1960-12-13 Rca Corp Loudspeaker magnetic field structure
US3092694A (en) * 1959-02-16 1963-06-04 Rca Corp Loudspeaker
US3106670A (en) * 1960-04-21 1963-10-08 Rca Corp Magnetic field structure for loudspeakers
US3801943A (en) * 1971-06-16 1974-04-02 J Bertagni Electoacoustic transducers and electromagnetic assembly therefor
US3874665A (en) * 1971-10-05 1975-04-01 Mcculloch Corp Ball putting cup and method of ejecting ball from same
US4635287A (en) * 1983-10-19 1987-01-06 Mutsuo Hirano Audio-frequency electromechanical vibrator
USRE32785E (en) * 1983-10-19 1988-11-15 Sanden Corporation Audio-frequency electromechanical vibrator
US4799266A (en) * 1986-11-25 1989-01-17 Kabushiki Kaisha Kenwood Electroacoustic converter
US20030219142A1 (en) * 2002-03-26 2003-11-27 Stompler Thilo Christian Speaker driver with detachable motor and basket
US7031490B2 (en) * 2002-03-26 2006-04-18 T C Sounds Inc. Speaker driver with detachable motor and basket
US7164777B1 (en) 2002-03-26 2007-01-16 Tc Sounds Inc. Speaker driver with detachable motor and basket

Also Published As

Publication number Publication date
BE469578A (es)
ES175452A1 (es) 1946-12-01

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